title: Roles of Na⁺/H⁺ exchanger type 1 and intracellular pH in angiotensin II-induced reactive oxygen species generation and podocyte apoptosis.
abstract: A growing body of evidence suggests that podocyte apoptosis is a major cause of decreased podocyte number, which leads to albuminuria and glomerular injury. The aim of this study was to clarify the molecular mechanisms of angiotensin II (Ang II)-induced apoptosis in cultured mouse podocytes. We examined the effects of Ang II (100 nmol/L) on apoptosis, superoxide anions, and cytosol pH in podocytes. For intracellular pH measurements, image analysis was conducted using confocal laser microscopy after incubation with carboxy-seminaphthorhodafluor-1. Superoxide anions and intracellular pH were elevated with Ang II treatment. Apoptotic cell numbers, as measured by TUNEL staining and caspase 3 activity, were also augmented in the Ang II-treated group. Pre-treatment with olmesartan (100 nmol/L, an Ang II type 1-receptor blocker), apocynin (50 μmol/L, NADPH oxidase inhibitor), or 5-N,N hexamethylene amiloride [30 μmol/L, Na⁺/H⁺ exchanger type 1 (NHE-1) inhibitor] abolished Ang II-induced podocyte apoptosis, whereas NHE-1 mRNA and protein expression was not affected by Ang II treatment. Moreover, Ang II increased NHE-1 phosphorylation. These results suggest that superoxide production, NHE-1 activation, and intracellular alkalization were early features prior to apoptosis in Ang II-treated mouse podocytes, and may offer new insights into the mechanisms responsible for Ang II-induced podocyte injury.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Kagawa University, Japan.
authors.forename: Ya
authors.initials: Y
authors.lastname: Liu
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hitomi
authors.forename: Suwarni
authors.initials: S
authors.lastname: Diah
authors.forename: Kazushi
authors.initials: K
authors.lastname: Deguchi
authors.forename: Hirohito
authors.initials: H
authors.lastname: Mori
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Masaki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakano
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobori
authors.forename: Akira
authors.initials: A
authors.lastname: Nishiyama
mesh_terms: D000804:Angiotensin II / Q000009:adverse effects*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D051379:Mice; D019255:NADPH Oxidases / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D050199:Podocytes / Q000166:cytology / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism / Q000502:physiology*
chemical_list: D027682:Cation Transport Proteins; D017382:Reactive Oxygen Species; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D000804:Angiotensin II; D019255:NADPH Oxidases; D053148:Caspase 3